In three-dimensional (3D) printing, a composition is laid down in successive layers of material to build a structure from a series of cross-sections of the structure. These layers may be produced, for example, from liquid, powder, paper, or sheet material.
In certain cases, a 3D printing composition is a thermoplastic material, which is extruded through a heated nozzle on to a platform and the nozzle moved with respect to the platform, successively building up layers of thermoplastic material to form a 3D object. After being extruded from the nozzle, the thermoplastic material rapidly cools. Depending in part on the temperature of the underlying thermoplastic layer, the overlying thermoplastic layer may or may not adhere well to the underlying thermoplastic layer. Furthermore, differential thermal expansion can cause stress to be built up in the finished object thereby diminishing the integrity of the object.